This invention relates to the field of switch actuators, and in particular to a membrane-mountable switch actuating device and to a method of mounting same to a membrane over a switch.
It is well known in the art to cover one or more pressure switches positioned upon a switch plate with a resilient cover. By applying manual pressure on the resilient cover directly over the switch, the resilient cover is depressed to actuate the underlying switch. Further, in the prior art a portion of the membrane switch cover surrounding the pressure switch may have been outwardly deformed from the adjacent exterior surface of the membrane as a raised convex or frusto-conical dome.
In applicant""s U.S. Pat. No. 6,064,019 a resilient membrane cover for electrical switch plates has one or more switch actuator buttons welded thereto. The head of the button projects above the exterior membrane surface. A switch actuation plunger, surrounded by a deformable annular sleeve depending at right angles from the head, projects outwardly of the inner surface of the membrane through an aperture. A circular portion of the upper surface of the membrane, generally surrounding the plunger, is subjected to heat and pressure to create a raised pillow-shaped embossed area. Heat and pressure are applied to the deformable sleeve to secure the button and membrane together, as by riveting.
The switch plate generally has a depression corresponding to the circular deformed area of the membrane, permitting the circular raised portion of the membrane to be slightly depressed during switch actuation and, when released, to return the button to a non-depressed position.
It has been found that the current method of riveting an actuator button with an integral deformable sleeve to the resilient membrane, by applying heat, in a temperature range of 120 degrees Celsius to 300 degrees Celsius with sufficient pressure to the deformable sleeve generally against the underside of the circular domed portion of the cover membrane, tends to shrink the raised portion of the membrane with a resultant decrease in its height. The inherent resilient property of the polyester or like material still allows the button to be returned to non-depressed position after use.
Further, after time, it has been found that where the cross sectional shape of the deformable sleeve and the aperture in the membrane are circular, the button will loosen and the button will tend to rotate out of position. Also, when the button loosens the rotation may cause the polyester cover to quickly cut into the shaft of the button. Preventing rotation helps to prevent this. Further such out-of-position rotation may tend to render buttons formed as pictograms or with international symbols more difficult for the user to understand or they may become meaningless to the user.
The switch actuator of the present invention comprises a separate cap and connector which are assembled through an aperture formed in a resilient membrane which provides a switch cover. The resilient membrane has an exposed exterior surface and an opposite interior surface. The membrane is mountable, by gluing or the like of the interior surface to a switch plate having one or more pressure actuated electrical switches mounted thereto. The switch cover has one or more non-circular button-receiving apertures. A portion of the membrane immediately surrounding the button receiving apertures may be outwardly deformed as a circular frusto-conical dome. In a further aspect the dome may be a separate component adapted to be non-rotationally received within an aperture formed in the switch cover.
A switch actuator is positioned within each button-receiving aperture formed in the switch cover. The actuator has a cap, which may be formed as a pictogram, for example a polygon containing three sides, which represents a directional arrow. The cap of the actuator is centered over the aperture formed in the membrane and contains a recess on its underside. A connector having an upstanding head conformably shaped to the cap recess and membrane aperture is insertable through the membrane aperture to be secured within the recess on the underside of the cap.
In a further aspect, the switch actuator may be a toggle type switch actuator, where an accessible elongated cap contains a projecting head, formed medially on its underside. One or more positioning pins depend from the underside of the head and are adapted to be inserted through similarly shaped apertures formed in the flexible membrane switch cover to extend into recesses formed in the switch. A connector positioned adjacent the interior surface of the cover is secured to the cap by means of a suitable fastening means such as adhesive or screws to firmly retain between them a portion of the cover.
In summary, the switch actuating device of the present invention includes a base plate, a flexible cover and a switch actuator. The base plate has at least one aperture therethrough. The flexible cover is mounted onto the base plate so as to cover over the aperture in the base plate. The cover has at least one aperture therethrough. The aperture or plurality of apertures in the cover each overlie or are aligned with, so as to be coextensive with, the apertures in the baseplate. As used herein, reference to first apertures is a reference to apertures in the baseplate. Reference to second apertures is a reference to apertures in the cover.
A switch actuator is rigidly mounted to the flexible cover so as to be journalled at least partially through the first aperture and through the second aperture, one actuator per first aperture. The switch actuator includes a cap and a base. The cap and the base are disposed on opposite sides of the cover. The cap and the base are mounted to one another so as to sandwich the cover between the cap and the base. The second aperture is formed as a socket means for mating with a corresponding plug means between the cap and the base for inhibiting rotation of the switch actuator relative to the cover in a plane substantially parallel to the cover.
In one embodiment, the plug means includes a non-cylindrical shaft extending between the cap and the base and the socket means is the second aperture when sized to fit snugly around the shaft and shaped to correspond in shape to the shaft. The shaft is a plunger generally perpendicular to the cover for translation orthogonally to the cover so as to actuate a switch mounted to the base plate on an opposite side of the base plate to the cover. The cap may include a cavity for receiving the shaft in mating engagement therein, wherein the cavity is shaped to correspond in shape and size to the second aperture. The base may include a flange for extending around the shaft so as to sandwich the cover under the cap. The cap is shaped so as to provide an opposed facing bearing surface to the flange when sandwiching the cover.
The cover may be a flexible membrane and formed as a resilient dome concentrically around the first and second apertures. Alternatively a resilient dome member may be mounted between the cap and the cover concentrically around the first and second apertures.
In a further embodiment, the plug means includes a spaced apart pair of shafts and the socket means a corresponding pair of second apertures. The pair of shafts are sized for snug mating journalled through the pair of the second apertures. The pair of shafts are mounted in the pair of second apertures so as to sandwich the cover therebetween to provide a hinge for rotation of the cap in a rocker motion about the hinge.
The base may extend through the first aperture into proximity to a switch mounted to the base plate on an opposite side of the base plate to the cover.
The cap may be elongate in a direction perpendicular to a hinge line of the hinge. Again, the cover may be a flexible membrane. The pair of shafts may be parallel and rigidly mounted to the cap.
In the method of mounting a switch actuating device according to the present invention the method includes the steps of providing the above described device, aligning the plug means with the at least one second aperture and journaling the plug means through the at least one second aperture so as to mate the cap to the base and sandwich the cover therebetween.